Fig. 2

 Potentials of mean force (PMF) as a function of surface separation distance (SSD) for TGTG-X-GTGT peptides on the silica glass surface shown as three separate curves in each plot: based on (i) unmodified Lennard-Jones (LJ) (vdW) and Coulomb (electrostatic) parameters (green circles) using the existing CHARMM parameter set; (ii) vdW only (i.e., zero charge on surface atoms; red squares); and (iii) electrostatics only (i.e., LJ well-depth (ε)<<kT on surface atoms; blue triangles) for (a) X = Phe (F), (b) X = Trp (W), (c) X = Val (V), and (d) X = Lys (K)